Proximity services (ProSe) may support device-to-device (D2D) communication in a cellular technology ecosystem. ProSe may rely on the proximity between two or more devices, (e.g., wireless transmit/receive units (WTRUs), user equipment (UEs), mobile stations), and allow specific commercial and social applications, network offloading, or public safety direct communications. Other alternatives, such as Wi-Fi or Bluetooth, may also support D2D communication, but they may operate on a license-exempt band, and thus they may be subject to higher interference and lower quality of service (QoS). ProSe may use D2D discovery and various communication procedures to address these issues.